FIG. 1 schematically shows a dedicated breast CT (“DBCT”) system 10, which is a medical imaging system designed to conduct CT on human breasts. The DBCT system 10 has a table 11 with a hole 12 therein, an X-ray source 13, and an X-ray detector 14. The table 11 is configured to support a patient thereon. During imaging, a patient lies on the table 11 face down on the table 11, with at least one of her breasts 99 projecting through the hole 12. The X-ray source 13 and any suitable optical components direct an X-ray beam toward the breast 99. The X-ray detector 14 is positioned to capture an image composed of X-ray that has passed through the breast 99. The X-ray source 13 (and optionally the X-ray detector 14 as well) may rotate around the breast 99.
A DBCT system may use an X-ray beam having large divergence in both the first direction and the second direction. Namely, the X-ray beam in a DBCT system may be cone-shaped. Therefore, the X-ray detector in a DBCT system may be a two-dimensional array of detector modules. In contrast, a conventional whole body CT system may use an X-ray beam having large divergence in the first direction and little divergence (e.g., 2° or less) in the second direction orthogonal to the first direction. Namely, the X-ray beam in a conventional whole body CT system is fan-shaped. Therefore, the X-ray detector in a conventional whole body CT system is usually strip-shaped, e.g., a row of detector modules.
A DBCT system may not need compression of the breast, which reduces the adverse effect of overlapped tissue caused by compression (e.g., in mammography). The slice sensitivity of a DBCT system may be essentially constant with respect to the breast diameter, and thus the resolution is consistent across any desired plane.